1. Field of the Invention
The present invention relates to a transmission line for high-speed signals in semiconductor integrated circuits, and a semiconductor device using the same.
2. Description of the Related Art
In recent years, speeds of semiconductor integrated circuits have been increasing, whereby microprocessors that operate at a clock speed of several GHz and high frequency circuits operating at several GHz have been achieved. The prevention of a cross talk between signal lines and attention for a high frequency signal response including line inductance are necessary for transmitting signals in a semiconductor integrated circuit at a GHz level. A coplanar waveguide or a microstrip line is a representative transmission line for transmitting high frequency signals.
An example of applying the coplanar waveguide to a clock line in a semiconductor integrated circuit has been reported (see F. Ishihara, Proceedings of ASP-DAC2000, pp. 647–652, 2000).
Furthermore, the microstrip line is generally applied to a printed board and the like. There is also an example of a structure of the microstrip line for reducing parasitic capacitance in a semiconductor integrated circuit (see M. Mizuno, IEEE ISSCC 2000, pp. 366–367, 2002).
A line width may be increased in order to decrease the line impedance for ultra high-speed signal transmission. However, by increasing the line width, a coupling effect between signal lines in the upper and lower layers relatively increases, and an effect of cross talk noise becomes a problem. Furthermore, an error may increase in the line impedance of additional signal lines predicted prior to wiring processing.
In the microstrip line, a ground plane that forms a return path requires a large amount of wiring resources, and may be a large obstacle for general signal lines.